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The Immune System
Antigen: Anything the body can not recognize.
eg) a splinter or a virus
Pathogen: An organism or substance that causes
disease.
Four Ways to Receive Infectious Diseases
Direct contact: Shaking hands
Indirect contact: Being near someone when
they cough
Water and food
Animal bites
1st line of defence:
Skin, mucus, tears, ear wax, nose hair, etc.
prevent pathogens from entering your body.
The gastric juices in the stomach destroy
pathogens which you swallow.
Innate Immune Response:
Inflammation: Fluid, cells and dissolved
substances flow to the site of infection causing
redness, swelling, and fever.
Increased numbers of phagocytes, white
blood cells that swallow invading cells.
Acquired Immune Response:
B cells: Recognize antigens in the body and
produce specific antibodies to fight them. The
antibodies attach to the antigens and stop
them from getting into body cells or flag them
for destruction by phagocytes.
T cells: Attach themselves to infected cells and
destroy them.
B and T cells work against specific pathogens,
when you get a disease for the first time it can
be difficult for the body to make the right B
and T cells to fight it. After the body has
fought off the disease some of these B and T
cells remain in the body and if you are ever
infected with the same disease again they
make copies of themselves to easily fight off
the pathogen. This is called active immunity.